Silencing calreticulin gene might protect cardiomyocytes from angiotensin II-induced apoptosis

Role of PLC/IP3 /IP3 R axis in excess molybdenum exposure induced apoptosis in duck renal tubular epithelial cells

Excess molybdenum (Mo) is harmful to animals, but its nephrotoxicity has not been comprehensively explained. To appraise the influences of excess Mo on Ca homeostasis and apoptosis via PLC/IP3 /IP3 R axis, primary duck renal tubular epithelial cells were exposed to 480 μM and 960 μM Mo, and joint of 960 μM Mo and 10 μM 2-APB or 0.125 μM U-73122 for 12 h (U-73122 pretreated for 1 h), respectively. The data revealed that the increment of [Ca2+ ]c induced by Mo mainly originated from intracellular Ca storage. Mo exposure reduced [Ca2+ ]ER , elevated [Ca2+ ]mit , [Ca2+ ]c , and the expression of Ca homeostasis-related factors (Calpain, CaN, CRT, GRP94, GRP78 and CaMKII). 2-APB could effectively reverse subcellular Ca2+ redistribution by inhibiting IP3 R, which confirmed that [Ca2+ ]c overload induced by Mo originated from ER. Additionally, PLC inhibitor U-73122 remarkably mitigated the change, and dramatically reduced the number of apoptotic cells, the expression of Bak-1, Bax, cleaved-Caspase-3/Caspase-3, and notably increased the expression of Bcl-xL, Bcl-2, and Bcl-2/Bax ratio. Overall, the results confirmed that the Ca2+ liberation of ER via PLC/IP3 /IP3 R axis was the main cause of [Ca2+ ]c overload, and then stimulated apoptosis in duck renal tubular epithelial cells.

Crosstalk between the renin-angiotensin system and the endoplasmic reticulum stress in the cardiovascular system: Lessons learned so far

The renin-angiotensin (Ang) system (RAS) is a complex hormonal system present locally in several tissues such as cardiovascular organs. RAS deregulation through overactivation of the classical arm [Ang-converting enzyme (ACE)/Ang-II/Ang type 1 receptor (AT1R)] has been linked to the development of cardiovascular diseases and activation of endoplasmic reticulum (ER) stress pathways. The ER stress is a condition that, if unresolved, might lead to heart failure, atherosclerosis, hypertension, and endothelial dysfunction. Accumulated evidence has shown that the RAS modulates the UPR activation. Several studies reported increased ER stress markers in response to Ang-II treatment, in both in vivo and in vitro models. Evidence has also pointed that targeting the RAS classical arm through RAS blockers, gene silencing or genetic models leads to lower levels of ER stress markers. Few studies demonstrated protective effects of the counter-regulatory arm (ACE-2/Ang-(1-7)/Mas receptor) over ER stress. However, the crosstalk mechanisms between the arms of the RAS and ER stress remain unclear. In this review, we sought to explore the classical arm of the RAS as a key mechanism in UPR activation and to suggest a possible protective role of the counter-regulatory arm in mitigating ER stress.

Silencing of CRT relieves Ang II-Induced injury of HUVECs with insulin resistance

In this study, we investigated the effects of Angiotensin II (Ang II) on insulin-resistant endothelial cells. High glucose and insulin at series of concentrations were used to induce IR in Human Umbilical Vein Endothelial Cells (HUVECs). Successful IR induction was confirmed according to glucose consumption and glycogen content levels. Cell morphology was observed under a microscope. Expression levels of Ang II and Calreticulin (CRT) were measured by ELISA, qRT-PCR and Western blot as appropriate. Cell viability and apoptosis were measured by CCK-8 assay and flow cytometry, respectively. HUVECs with IR were exposed to Ang II at series of concentrations, and then the cell viability, apoptosis and CRT were detected. Rescue assays were performed by transfection of siCRT or overexpression of CRT with or without Ang II stimulation into the HUVECs with IR. Expressions of cell apoptosis-related proteins Bcl-2 and Bax were measured by qRT-PCR and Western blot. Glucose (33.3 mmol/L) and insulin (4 µmol/L) induced significantly strong IR to the HUVECs, with a pathological appearance. Levels of Agn II and CRT were both up-regulated by IR. Cell viability of HUVECs was slightly reduced after IR induction for 2 h, and cell apoptosis rate was increased. In addition, Ang II (10^-7 mol/l) suppressed cell viability and glucose uptake, promoted cell apoptosis and increased CRT, and these effects could be weakened by silencing CRT. Thus, we preliminarily proved that Ang II up-regulates CRT, and CRT knockdown can relieve Ang II-induced injury of HUVECs with IR.

Calreticulin regulated intrinsic apoptosis through mitochondria-dependent and independent pathways mediated by ER stress in arsenite exposed HT-22 cells

Arsenic is a naturally occurring environmental toxicant. Chronic exposure to arsenic is linked with neurological damage. Although the mechanisms remain to be elucidated, it is currently believed that neural cell apoptosis is one of the underlying mechanisms of arsenic-induced neurotoxicity. Calreticulin (CRT) is a quality control chaperone located in the lumen of the endoplasmic reticulum (ER), which participates in many signaling pathways including apoptosis. However, the role of CRT in apoptosis is controversial. Whether CRT plays a role in arsenite-induced apoptosis and the relationship between CRT and ER stress-mediated apoptosis have not been mentioned before. In this study, we found that CRT expression as well as the cell apoptosis levels increased in a dose dependent manner upon arsenite exposure in HT-22 cells, a mouse hippocampal neural cell line. In addition, arsenite exposure resulted in the up-regulation of ER stress indicator GRP78 and ER stress-related proteins including p-PERK, ATF4, CHOP, calpain2 and cleaved caspases-12, accompanied by the down-regulation of Bcl-2 and up-regulation of Bax and cleaved caspase-3. Silence of CRT remarkably alleviated arsenite-induced apoptosis and reversed the expression of the proteins above. Our findings confirmed the role of CRT in the induction of apoptosis upon arsenite exposure and suggested that CRT mediated the intrinsic apoptotic cell death including both mitochondria-dependent (PERK/ATF4/CHOP/Bcl-2) and independent (calpain2/caspases-12) pathways initiated by ER stress, which we believed to be a previously undocumented property of arsenite-induced apoptosis.

Calreticulin expression in human cardiac myocytes induces ER stress-associated apoptosis

The global burden of heart failure following myocardial ischemia-reperfusion (IR) injury is a growing problem. One pathway that is key to understanding the progression of myocardial infarction and IR injury is the endoplasmic reticulum (ER) stress pathway, which contributes to apoptosis signaling and tissue death. The role of calreticulin in the progression of ER stress remains controversial. We hypothesized that calreticulin induction drives proapoptotic signaling in response to ER stress. We find here that calreticulin is upregulated in human ischemic heart failure cardiac tissue, as well as simulated hypoxia and reoxygenation (H/R) and thapsigargin-mediated ER stress. To test the impact of direct modulation of calreticulin expression on ER stress-induced apoptosis, human cardiac-derived AC16 cells with stable overexpression or silencing of calreticulin were subjected to thapsigargin treatment, and markers of apoptosis were evaluated. It was found that overexpression of calreticulin promotes apoptosis, while a partial knockdown protects against the expression of caspase 12, CHOP, and reduces thapsigargin-driven TUNEL staining. These data shed light on the role that calreticulin plays in apoptosis signaling during ER stress in cardiac cells.

Analysis of Comparative Proteomic and Potent Targets of Peniciketal A in Human Acute Monocytic Leukemia

BACKGROUND

Peniciketal A (Pe-A), a spiroketal compound, shows potent anticancer activities in human acute monocytic leukemia. However, the detailed mechanisms and potent targets of Pe-A remain largely unexplored. Here, we investigated the differentially expressed proteins between the Pe-A-treated group and the control group on human acute monocytic leukemia cell line THP-1.

METHODS

The DEPs were analyzed by the liquid chromatography-tandem mass spectrometry (LC-MS/MS) with TMT label. The function and feature of the identified proteins were analyzed by the bioinformatic analysis. Western blotting was used to evaluate protein expression.

RESULTS

The DEPs were primarily sub located in the cytoplasm and the nucleus by regulating 21 pathways enriched through the Kyoto Encyclopedia of Genes and Genomes (KEGG). Moreover, we preliminarily demonstrated that glucose-6-phosphate 1-dehydrogenase (G6PD), prolow-density lipoprotein receptor-related protein 1 (LRP1) and Calreticulin (CALR) might be the potent targets of Pe-A on death induction of THP-1 cells.

CONCLUSION

Collectively, this study not only provides a global proteomic profile as the supplementary data of our previous studies but also provides interesting information that Pe-A may exert more bio-activities.